A system for processing an electromagnetic signal can be used for transmitting an electromagnetic signal and/or for receiving an electromagnetic signal. The electromagnetic signal may be transmitted and/or received via an antenna system. In a system that is used for receiving an electromagnetic signal, the antenna system receives electromagnetic waves that are converted into an electrical signal for further processing, in particular an electric current. The electrical signal is transmitted via a transmission path to a radio receiver for analyzing purposes.
Due to structural restrictions at the installation site of the system, customers using such a system may have to bridge a long distance between the antenna system and the radio receiver, for instance 10 to 100 meters or even more. Accordingly, a transmission path has to be used that ensures high information security, high interference immunity and very good performance, simultaneously. This means that persons being not authorized shall not have any access to the information transmitted via the transmission path (high information security). Further, no electromagnetic radiation shall be emitted from or irradiated into the transmission path (high interference immunity), in particular parasitic electromagnetic interferences. In addition, a wide dynamic range, a low noise factor and a high linearity shall be ensured by the system (very good performance). In general, the very good performance corresponds to very good radio frequency data processed by the system.
In the state of the art, several systems are known for processing an electromagnetic signal even though a long distance has to be bridged between the antenna system and the radio receiver. For instance, systems are known that use a coaxial transmission line for transmitting radio frequency signals received via the antenna system as this ensures that broadband signals can be transmitted while a high linearity is achieved. However, coaxial transmission lines have a high attenuation that is frequency dependent.
Further, systems are known that transmit the information digitally, for instance via a local area network transmission line (LAN connection), as the signals can be transmitted over long distances in a lossless manner. However, the information security is low as an existing network has to be used wherein unauthorized persons may break into that network. In addition, a local area network connection can only be used for connecting the radio receiver with a control and/or analyzing unit. Thus, the radio receiver has to be installed close to the antenna system.
It is also known in the prior art to use fiber optic cables for transmitting radio frequency signals received via the antenna system. This is called radio frequency over fiber (RFoF). Thus, the electric signals obtained by the antenna system have to be converted into an optical signal that is transmitted to the radio receiver wherein the optical signal is reconverted into an electrical signal prior to the radio receiver. The optical transmission path ensures low attenuation (loss) and high information security. However, an optical transmission path has a limited dynamic range, a high noise factor as well as a high non-linearity resulting in unwanted harmonics.